Crosslinked composite membrane and process for producing the same

Abstract

A crosslinked composite membrane having high permeation velocity and separation factor and a process for producing the same. The membrane comprises a skin layer comprising a crosslinking reaction product of a water-soluble polysaccharide having a sulfonate group and/or a sulfonic acid group and a polyfunctional melamine compound the crosslinked composite membrane can be formed on a porous base such as an ultrafilter.

What is claimed is: 
     
       1. A process comprising producing a crosslinked composite membrane by the steps of: applying a crosslinking solution containing reactants which comprise a water-soluble polysaccharide having a sulfonate group and/or a sulfonic acid group and a polyfunctional melamine compound to a porous base;   effecting the drying of the crosslinking solution and the crosslinking of the reactants simultaneously to form a skin layer having a crosslinked structure formed by covalent bonds on the porous base; and   repeating said process steps.   
     
     
       2. The process according to claim 1, wherein said process steps are repeated at least twice. 
     
     
       3. The process according to claims 1 or 2, wherein the crosslinking solution is applied by immersion or by means of a bar coater, roll or doctor blade. 
     
     
       4. The process according to claims 1 or 2, wherein the crossing is effected by heating or irradiation with U.V. rays or electron beams. 
     
     
       5. The process according to claim 1, wherein said crosslinking solution has a pH of 6 or below. 
     
     
       6. The process according to claim 1, wherein said crosslinking solution has a pH of 4 or below. 
     
     
       7. The process according to claim 1, wherein the porous base is an ultrafilter. 
     
     
       8. The process according to claim 1, wherein the water-soluble polysaccharide is sulfoethylcellulose or an alkali salt thereof. 
     
     
       9. The process according to claim 1, wherein the polyfunctional melamine compound is n-methoxymethylmelamine, n being di to hexa. 
     
     
       10. The process according to claim 1, wherein the polyfunctional melamine compound is an n-methylolmelamine, n being di to hexa. 
     
     
       11. The process according to claim 1, wherein the polyfunctional melamine compound content is 3 to 60 wt. %. 
     
     
       12. The process according to claim 1, wherein the polyfunctional melamine compound content is 10 to 40%.